Korea International Trade Association (KITA) statistics show that the import of circular-knitted clothes has suddenly increased since 2000; they have increased by 24.5% each year for 2000-2004 and by 8.2% for 2005-2009. In addition, a Korea Apparel Industry Association survey showed that more than 50% of young people in their 20s and more than 40% of mid-aged people in their 30s-40s wore T-shirts (the most frequently worn and/or regarded as the most comfortable item among knit clothes). This portion is expected to increase in the future; however, insufficient research has been conducted on the characteristics of product development and production, knit T-shirt pattern development (Park, 2011), and consumer purchase patterns and behavior for knit clothes. The evaluation criteria for knit clothes generally vary depending on the demographic characteristics of consumers (Kotler & Armstrong, 2006). This study conducted a wearing trends survey for circular-knitted T-shirts and fit satisfaction based on 318 male and female consumers in their 20s-30s. The results provide information on the basic materials required to produce circular-knitted T-shirts.